Electrooptical image production



28, 1934- J. H. BOLLMAN 1,971,674

ELECTROOPTICAL IMAGE PRODUCTION Filed July 25. 1931 3 Sheets-Sheet l TAPE FULLER a PERFORA TOR TER AITENUATOR .J H. BOLLMAN 44% 1934 J. H. BOLLMAN 1,971,674

ELECTROOPTICAL IMAGE PRODUCTION Filed July 25. 1931 3 Sheets-Sheet 2 //WE/\/ 0/? J h! BULL/WAN Fla. 2

1934- J. H. BOLLMAN 1,971,674

ELECTROOPTICAL IMAGE PRODUCTION Filed July 25. 1951 5 Sheets-Sheet 3 A TTD/P/VE) Patented Aug. 28, 1934 PATENT OFFICE ELECTROOPTICAL IMAGE PRODUCTION John H. Bellman, Woodcliff, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 25, 1931, Serial No. 553,098

7 Claims.

This invention relates to electro-optical systems and particularly to systems for reproducing pictures by the use of telegraph code signals.

The invention provides an improved system for the electrical transmission of pictures or the production of images at a distant point under control of transmitted current corresponding to the tone values of the elemental areas of a picture or other object. The amplitude of a periodically 10 varying current is controlled in accordance with the tone values of successively scanned elemental areas of a field of View, and the resulting varying current is utilized to control the operation of relay means set to respond when said varying current reaches a predetermined value.

In a specific embodiment of the invention herein shown and described for the purpose of illustration, means are provided for directing, upon a light sensitive element, a beam of light which is caused to vary in accordance with the tone values of the successive elemental areas of a picture or object, an image of which is to be produced. There is provided a rotating disc making a single revolution in the period required for t scanning a single elemental area and having apertures therein arranged along an arc of a circle for interrupting the beam of light at a high frequency compared to the frequency of scanning successive elemental areas so that a high frequency current modulated in accordance with the tone values of successively scanned elemental areas of the picture or object is produced in a circuit associated with the light sensitive cell. This modulated high frequency current, after being amplified by an alternating current amplifier which is preferably associated with a tuned circuit to increase the amplification eniciency, is impressed, through a transformer, upon ,a plurality of alternating current amplifying vac- 40 uum tubes connected in parallel and differently biased so as to operate over different ranges of impressed electromotive force, respectively. The output circuit of each of these vacuum tubes is coupled through a transformer to a plurality of rectifier vacuum tubes which are biased so as to operate over diiferent values of impressed electromotive force, respectively. An electromagnetic relay is connected in the output circuit of each of these rectifier vacuum tubes and these relays control the selection of code combinations of telegraph signals to be punched in a tape or transmitted directly, said .code combinations corresponding to the tone values of the elemental areas of a picture or object.

The apertures of the light interrupting disc are preferably omitted-over a portion of the circle so that the light beam is interrupted for a comparatively long period of time between the scanning of successive elemental areas, as disclosed; and claimed in a copending application of J. W. Horton, Serial No. 555,669, filed Aug. 7, 1931. In order to avoid the rapid increase in current which would normally occur following the period during which the light beam is interrupted for a comparatively long interval, and the resulting false operation of relays, the first few light apertures of the light interrupter disc following this portion of the disc which interrupts the light for a comparatively long interval are given a tapered characteristic so as to cause the amplitude of the photoelectric current to increase gradually to the amplitude determined by the tone values of the elemental area of the field of view being scanned. This may be accomplished by employing apertures of gradually increasing size or by covering a few of the apertures of constant size with a. film of gradually increasing transparency.

At the receiving station, a tape may be perforated similarly to the. tape at the transmitting station under control of the received telegraph 30 signals. This tape controls the actuation of a number of electromagnetic relays equal to the number of different tone values into which the field of view is analyzed at the transmitting station. These relays control the current through 5 a light valve or similar device, as by varying the resistance in circuit therewith, and this light valve controls the amount of emitted light to produce an image, for example, by exposing a light sensitive surface.

A detailed description of the specific embodiment of the invention mentioned above follows, reference being made to the accompanying drawings, in which Figs. 1 and 2 show diagrammatically the transmitting station of a code telegraph picture reproducing system in accordance with the present invention;

Fig. 3 shows diagrammatically the receiving station of a code telegraph picture reproducing system; and

Figs. 4 and 5' are plan views of apertured discs such as may be employed in connection with the apparatus shown in Fig. 1 for interrupting the scanning light beam.

Figs. 1,2 and 3, when placed side by side in order with Fig. 1 at the left, show a complete code telegraph picture transmission system. The picture which is to be reproduced is in the form of a negative film 10 of varying transparency mounted on the drum 11 of transparent material.

A beam of light from source 12 is focused upon a small spot on the film by means of the lenses l3 and 14 and, after passing through the film, impinges upon the photoelectric cell 15. The drum 11 on which the picture film is mounted is driven by motors 16 through gears 17 to cause it to rotate and at the same time move'slowly in an axial direction. The light beam impinging upon the picture film 10 thus scans the picture along a helical path. The scanning light beam is interrupted by an apertured disc 18 driven by motor 16 through gears 19 andv 20. I produced in the circuit of the photoelectric cell 15 a pulsating current having-an alternating component, the frequency cf-which=-is-controlledin accordance with the rateof interruption of the light beam and the amplitude of whichvaries in accordance with the tone values of the successively scanned elemental areas of thepicture. The photoelectric current is amplified by the vacuuin'tube amplifier 21 in the anode circuit of which is 'a tuned' circuit comprising a condenser ZZandtheprimary winding'of transformer 23 tunedto the'frequency of the alternating component er the; photoelectric current. The secondarywinding'of transformer 23 is connected to an alternating current amplifier comprising 'vacuum' tubes 24 and 25, transformers 26 and 2'? and aniadjustable attenuator 28. f The output circuit of the'ar'np-liiying vacuum tube is connected through transformer 29 to the input circuits 'of amplifying vacuum tubes 30 to 33 inclu Thes'e'vacuum tubes'have' different grid The grid of vacuum tubeBO is biased by the elec- "tromotive force of battery 34 the grid ofvacuum "tube"3l' is'bia'sed by the sum of the electroinot'ive 'f'orces of'batterie's 34 and 35; the g rid o'f vacuum tube 32 is biasedby the sum of theielec'tromotive forces of batteries 34,35and'36 and that of tube "33 is'biased by the sum of the electromotivefo'rces of batteries'34' to' 37, inclusive. The vacuum tubes "30 to 33,"inclusive'also have different sources of anode-potential, the" tube 30 having the-anode potential equal to the electromotive force createryf38, tiibe3l' having the sum of the electrometiire' forces of'batteries'38-and 39, tube'32 the sum of" the electrornotive forces of batteries'38, 39 and '40 and.tube"33 having the electroniotive forces of batteries38to '41 inclusive. "When an elemental area of the negativeipicture representation 10 or relatively dark "tone value is being scanned, the" transmitted alternating current and the corresponding alternating electrornot-ive iorce impressed upon the input circuits of vacuum tubes 30'to 33, inclusive is of'low amplitude.

"Asa'resu'lt a varying current'fis caused new in theprimary" winding of transformer 42 "and a corresponding alternating electrornotive force' in duced in the secondary winding of'thisYtra'nr fo'rmer. 'Wh'ei'ian elemental area of somewhat lighter tone value is being scanned the alternatingelectromotive force impressed upon the input circuits of vacuuin'tubes 30 to33-is ,of, correspondinglygreater amplitude and vacuum tubes 30 and 31 are operated to causean electronic't'ive "force to 'be'induced'in the'secondary windings of transformers 42'jand 43. "When" the'to'ne value of theelemental area beingjsc'annedis still light- There isthusfor elemental areas of very light tone value all four vacuum tubes 30 to 33 operate. When vacuum tubes 30 to 32, inclusive operate an alternating electromotive force is induced in the secondary windings of transformers 42 to 44, inclusive and when all four vacuum tubes operate an alternating electromotive force is induced in the secondary windings of all four'transformers -42 to 45, inclusive. We may therefore consider the tone values of the picture as being grouped into four ranges of value, for example, very dark, dark, light and very light, and one, two, three or allfour ofthe vacuum tubes 30 to 33 will be operated according to the group into which the tone valueoi' the elemental area being scanned is classified. -Eachoi these groups may be subdivided *into as many groups as desired, for example,

four. It is apparent that not only will one, two, three or four of the vacuum tubes 30 to 33 be operated as elemental areas falling in different groups of tone values, respectively, are being scanned, but also that thefaiternating electromotive forces induced in the secondary windings of transformers 42 to 45, inclusive vary over a range of values in accordance with the variations in tone value occurring within each of the four groups of tone values.

v The secondary windings of transformers 42 to 45, inclusive, are connected to the] input ciruits of four different groups of rectifier vacuum tubes, respectively, the first group comprising vacuum tubes 46 to,49,"inclusive,' the secondgroup comprising vacuum tubes 50 to 53, inclusive,the

'third group comprising vacuum tubes 54 to' 5'7,

inclusive, and the fourth, vacuum tubes 58 tov 61, inclusive. Relays 62 to 77, inclusive, are connected, respectively, in theano'de circuitsof the vacuum tubes 45 toflfil, inclusive. ,One or more of the rectifier vacuum tubes of the first group will "be operated whenever the amplifier vacuum tube.

30 is operated, one or rnore of the second group whenever vacuum tube 31 is operated, one or more of the third group whenever vacuum tube "32 is operated and one or more of the'fourth groupwvhenever vacuum tube '33 is operated.

with 'difierent grid'biasing and anode potentials,'respectively, similarly to the vacuum tubes 30 to'33, inclusive, so that they operate" to cause the anode current to reach a predetermined very dark elemental area of the negative picture 10' is being scanned and'that the attenuation The vacuumtubes of each group are provided amplitude in response to input signal electromotive forces of diiferent amplitudes, respectively. Suppose, for example, thatablack or of 'the'variable attenuator 28'is, progressively reduced until current flows in the anode circuits of vacuum tubes 30 and 4 6, the current in the anode circuit of the vacuum tube 46 having sufiicient amplitude to cause the operation of relay 62 and the closure of the circuit through contact '78. Then as elemental areas of lighter tone values are scanned, the current in the anode circuit of vacuum tube 30 will increase in amplitude until vacuuin'tube '47 and its associated relay 63 are operated to close contact'lg in addias to vacuum tuhel46 and relay 62. As further increases in current in the anode circuit of 'vacuumtubeto take place vacuum tubes 46,

"er; vacuum tubes30' to 3,2,inclu'sive operateand elem ntal area 4 of still lighter .tone. value is output circuit of vacuum tube 50 so as to cause the, operation of relay, 66 to close contact 82. It is thusseen that we may divide the total range of picure tone values into. 16 groups and the picture will be reproduced in 16 tonevalues, one

, corresponding to the range of tone values of each ,ofthe groups. When a black orvery dark elementalarea is scanned, relay 46 will operate;

. when an elemental area of slightly lighter, tone valueis scanned, relays 62 and63 will operate simultaneously, etc. until all of the relays 62 to :77 are operated, in response to the scanning of a very light or. white elemental area, to cause the .'-closure of contacts 78 .to 92inclusive and the J 'openingof contacts 93 to 98 inclusive.

..inclusive, through one, or more of the punch magnetsgl to 5 inclusive of the tape perforator 99, to the grounded battery 100, thus causing the When one or more of the relays 62 to 77 are operated, a. circuitis completed from ground 9 through, one ,or more of the leads 201v to 205 operation of different combinations of punch magnets 1 to 5 in accordance with the operation of the relays 62 to 77, inclusive, and punching ,code combinations in a tape 117 in accordance with the tone values of the, successively scanned elemental areas of the picture 10. The motor 16 which drives the drum 11 and the light interrupting disc 18 also drives a cam operated punch 118 through gears 119 for punching. the tape 117. with code combinations corresponding to *the tone values of. the successive elemental areas of the picture 10, one code combination being punched. each time the light interrupting disc 18 makes a single revolution. The dififerent combinations of punch magnets 1 to 5 which are energized in response to the operation of different groups of relays 62 to 77 respectively, are indicated in the following table:

Punch magnet energized Tone value of negative picture Relays operated i The tape 117 is' fed into a tape transmitter 120 which transmits'code telegraph signals corresponding to the code punchings in the tape 117,

over a telegraph conductor 121, such as a submarine cable, for example. Instead of punching a tapeffor controlling the transmission of a code signals over a line, thecode combinations may be set up bymeans of relays taking the place of the punch magnets 1 to 5 which, together "with a commutating device, control the transmission of the c'odesignals directlywithout first punching a tape. a Anysuitable system may be employed for reproducing a picture under control of the received code telegraph impulses. shown in Fig. 3, the codetelegraph signals sent .over line 121 are impressed upon a tape reperforator 122 forjcontrolling the. punching of At the .receiving station current from a suitable source vrnitter 124 which is similar to the transmitter 120 at the transmitting station, for roducing code signals which are impressed on one or more of the relays 101 to 165, inclusive, in accordance with the operation of the contacts of the tape transmitter 124. The combination of the relays 101 to 105, inclusive, which are energized in accordance with a given code signal, will correspond to the combination of punch magnets 1 to 5, inclusive, which are energized at the transmitting station for controlling the production of this code signal. One or more of the resistance elements 162 to 177 inclusive are shortcircuited in accordance with the combination of relays 101 to 105 which are energized, the number of short-circuited resistance elements corresponding to the number or" relays 62 to 77 which are energized at the transmitting station. The following table indicates the resistance elements which are short-circuited when various combinations of relays 101 105 are energized.

Tone value of posi- Resistance eletive picture to be Relays operated ments shortreproduced circuited White 101 162.

Do.-. 101 and 102 162 and 103. Do... 101, 102 and 103.-.. 162170 104. D0... 101, 102, 103 and 162 to 165 D0-.- 101, 102, 103, 104 and 1 162 to 160 Do-.- 102, 103, 104 and 105-.. 162 to 107 D0-.- 103, 104, and 105 162 to 168 Do-.- 101 and 105 162 to 169 D0-.. 105 162 to 170 Do. 101 and 105 162 to 171 Do 101, 102 and 100.... 162 to 172. Do. 101, 102, 103 and 105 162 to 173. Do. 102, 103 and 105. 162 to 174. D0. 103 and 105 162 to 175. Do 101, 103 and 105..." 162 to 176.

Black or very dark. 101, 103, 101 and 105 162 to 177.

The number of resistance elements which are short-circuited controls the amplitude of the flowing through a light valve 178 to control the size or" the light aperture therein. The source of current for actuating the light valve may, for example, he a source of alternating current 179 having a period which is low compared with the time required for reproducing a single elemental 01 a picture. The tape 123 is fed into the tape transmitter 124 for causing the production of current impulses in relays 101 to 105 at a desired rate and a picture drum 180 which holds a light sensitive sheet 181 is driven at a corre-- sponding rate under control of a driving motor 182 and the gears 183 and 184, respectively. Light from source 185 is directed upon a small spot of the light sensitive sheet 181 at any particular instant by means of the lenses 186 and 187. The picture drum is caused to rotate and at the same time to be moved slowly in an axial direction, similarly to the drum 1]. at the transmitting station, to cause he successively illuminated spots on the picture receiving surface to describe, in effect,'a helical path. The intensity of the light reaching successive elemental areas of the picture receivin surface 181 is controlled in accordance with the amplitude of the current flowing through the light valve 178 w ich in turn is controlled in accordance with the received code signals which determine the number of r sistance elements 162 to 177 which become shortcircuited by the'actionof the relays 101 to 105. A

vacuum tubes difierently biased, respectively, and having a common input circuit connected to said source of alternating electrcmotive force for causing the operation of different combina-- tions, respectively, of said relays in accordance with the amplitude of the alternating electrometive force of said source, and means comprising a plurality of transformers for associating the output circuits of said vacuum tubes with said electromagnetic relays.

JOHN H. BOLLMAN. 

